Radio control valve for a continuously variable transmission

Abstract

A continuously variable transmission control system having adjustable driving and driven sheave assemblies (124,126) connected drivably by a torque transfer belt or chain (144), each sheave assembly having a fluid pressure operated servo with a pressure chamber, distribution of control pressure to one servo (150,158,162) effecting a transmission ratio adjustment, control of pressure distribution to the other servo (202,210) resulting in a clamping force, a ratio control valve (246) for controlling distribution of pressure to the ratio controlling servo to effect upshifts and downshifts, provision being made for stabilizing the ratio control valve by providing for flow entry to the ratio control valve that is unrestricted, flow distribution to the ratio controlling servo having a controlled restriction whereby stability of the ratio control valve is achieved, fluid displaced from the ratio controlling servo being adapted to circulate through the ratio control valve to the inlet side (372) of the control system pump (70,72).

Having described a preferred embodiment of my invention, what I claim and desire to secure by U.S. Letters Patent is: 
     
       1. A control system for a continuously variable transmission having a primary friction sheave assembly and a secondary friction sheave assembly, a drive belt drivably connecting said sheave assemblies, primary servo means for adjusting the pitch radius of said primary sheave assembly, secondary servo means for adjusting the pitch radius of said secondary sheave assembly; said control system comprising a pump, a control valve circuit connecting each servo means with said pump;   each sheave assembly including a pressure chamber of expansible volume, an increase in the pitch radius of one sheave assembly being accompanied by a decrease in the pitch radius of the other sheave assembly;   said primary servo means comprising an upshift pressure chamber and a downshift pressure chamber; and   a ratio control valve means in said valve circuit for controlling distribution of pressure to said upshift and downshift pressure chambers from said pump;   said ratio control valve means comprising a valve chamber, a movable valve spool in said valve chamber, a pair of valve lands with flow metering edges on said spool, flow exit ports in said valve chamber adapted to register with said flow metering edges, and flow inlet ports in said valve chamber at locations adjacent said lands whereby inlet flow to said valve chamber is unrestricted by said lands.   
     
     
       2. A continuously variable transmission for a vehicle having an engine comprising a primary sheave assembly connected drivably to said engine and a secondary sheave assembly connected drivably to a driven member, a drive belt drivably connecting said sheave assemblies, primary servo means for adjusting the pitch radius of said primary sheave assembly, secondary servo means for adjusting the pitch radius of said secondary sheave assembly; a control system for controlling transmission ratio comprising a pump, a control valve circuit connecting each servo means with said pump;   each sheave assembly including a pressure chamber of expansible volume, an increase in the pitch radius of one sheave assembly being accompanied by a decrease in the pitch radius of the other sheave assembly;   said primary servo means comprising an upshift pressure chamber and a downshift pressure chamber; and   a ratio control valve means in said valve circuit for controlling distribution of pressure to said upshift and downshift pressure chambers from said pump;   said ratio control valve means comprising a valve chamber, a movable valve spool in said valve chamber, said valve chamber having first and second ports communicating with said upshift chamber, third and fourth ports communicating with said downshift chamber, and outlet porting communicating with the inlet side of said pump;   said valve spool having flow metering lands registering with said outlet porting and with said second and fourth ports, the flow of fluid toward said valve chamber from said pump and toward said first port and said third port from said upshift and downshift chambers, respectively, being unrestricted by said lands.   
     
     
       3. The combination as set forth in claim 1 wherein said control system comprises an electronic controller including means responsive to operating variables of said transmission for developing a control pressure signal that is an indication of a commanded transmission ratio, said valve circuit including means for subjecting said valve spool to said control pressure signal whereby the position of said valve spool is determined by said control pressure signal. 
     
     
       4. The combination as set forth in claim 2 wherein said control system comprises an electronic controller including means responsive to operating variables of said transmission for developing a control pressure signal that is an indication of a commanded transmission ratio, said valve circuit including means for subjecting said valve spool to said control pressure signal whereby the position of said valve spool is determined by said control pressure signal. 
     
     
       5. A continuously variable transmission for a vehicle having an engine comprising a primary sheave assembly connected drivably to said engine and a secondary sheave assembly connected drivably to a driven member, a drive belt drivably connecting said sheave assemblies, primary servo means for adjusting the pitch radius of said primary sheave assembly, secondary servo means for adjusting the pitch radius of said secondary sheave assembly; a control system for controlling transmission ratio comprising a pump, a control valve circuit connecting each servo means with said pump;   each sheave assembly including a pressure chamber of expansible volume, an increase in the pitch radius of one sheave assembly being accompanied by a decrease in the pitch radius of the other sheave assembly;   said primary servo means comprising an upshift pressure chamber and a downshift pressure chamber;   a ratio control valve means in said valve circuit for controlling distribution of pressure to said upshift and downshift pressure chambers from said pump;   said ratio control valve means comprising a valve chamber, a movable valve spool in said valve chamber, said valve chamber having first and second ports communicating with said upshift chamber, third and fourth ports communicating with said downshift chamber, and outlet porting communicating with the inlet side of said pump;   said valve spool having flow metering lands registering with said outlet porting and with said second and fourth ports, a pump inlet flow passage connecting said inlet side of said pump with said third port, and flow directing means in said inlet flow passage for converting velocity pressure in said inlet flow passage into an increased static pressure at said inlet side of said pump thereby supercharging said pump.   
     
     
       6. The combination as set forth in claim 4 including a pump inlet flow passage connecting said inlet side of said pump with said third port, and flow directing means in said inlet flow passage for connecting velocity pressure in said inlet flow passage into an increased static pressure at said inlet side of said pump thereby supercharging said pump. 
     
     
       7. The combination as set forth in claim 6 including a sump and filter assembly, said inlet flow passage being in fluid communication with said sump and filter assembly, said flow directing means being adapted to induce filtered oil from said sump and filter assembly into said inlet side of said pump.